1. Field of the Invention
This invention relates to medical diagnostic testing, and more particularly to a medical test that determines the likelihood that chest pain symptoms can be attributed to the reflux of acidic gastric contents.
2. Description of the Prior Art
Gastroesophageal reflux is a common human condition arising from the backwash or "reflux" of stomach acid into the esophagus. Mild reflux with "heartburn" is a very common condition experienced by nearly everyone at one time or another. However, prolonged or repeated bathing of the esophagus with gastric acid may lead to gastroesophageal reflux disease or "GERD." GERD is a disease that produces symptoms and/or tissue damage secondary to the reflux of gastric contents into the esophagus. A primary symptom of GERD is heartburn.
The prevalence of GERD in the U.S. population is increasing and, at a minimum, effects approximately ten percent (10%) of the U.S. population. This segment of the population has heartburn daily. More than one-third of the U.S. population, however, is estimated to have intermittent heartburn symptoms. Left untreated, GERD may lead to esophagitis, an esophageal ulceration, stricture or a malignant tumor formation.
Early diagnosis is an important aspect in the successful treatment and prevention of the progression of GERD. While many patients experience heartburn-like symptoms during reflux, it is difficult to quantify the degree or extent of the reflux from the symptoms alone. Moreover, since the symptoms of GERD often mimic cardiac chest pain, the physician must confirm that the symptoms are in fact due to reflux and not to a cardiac condition. The treatment of GERD largely involves the suppression or neutralization of acid. An appropriate treatment should, therefore, only be initiated in patients in whom it can be determined that the symptoms are related to esophageal mucosal contact arising from the retrograde flow of acid from the stomach into the esophagus.
The majority of individuals with reflux symptoms such as heartburn are never seen by physicians. A smaller yet significant group of individuals has persistent symptoms of reflux without complications and is more likely to occasionally seek medical attention. The majority of individuals with mild GERD manage their condition through the use of antacids, while a growing number are tuning to acid suppression medications, which are now sold without prescription, such as cimetidine (Tagamet.RTM.), famotidine (Pepcid.RTM.), or ranitidine (Zantac.RTM.). The treatment of suspected GERD using prescription acid suppression medication is relatively expensive and costs the U.S. health care system billions of dollars each year. Furthermore, it is estimated that Americans spend nearly one billion dollars each year on antacids alone. Many antacid users as well as patients who are taking prescription acid suppression drugs do so on the presumption that they have acid-related symptoms which could lead to or indicate GERD.
In terms of diagnosing GERD, one known method, that is fairly sensitive, uses endoscopy in order to permit direct visualization of the esophagus. This examination may reveal erosions, ulcerations, exudates, strictures or other complications associated with GERD. However, only patients with daily heartburn and other associated GERD symptoms would be likely candidates for endoscopy due to the costs and inconveniences associated with the procedure.
Other known tests involve the measurement of the acidity of the patient's esophagus over an extended period of time. Various devices for ambulatory pH testing are known, such as that shown in U.S. Pat. No. 4,503,859, issued to Petty et al., and U.S. Pat. No. 5,117,827, issued to Stuebe et al.
Another method of establishing a presumptive diagnosis of GERD is to measure the pressure in the lower esophagus. A relatively low pressure (less than 10 mmHg) between the esophagus and the stomach provides reasonable evidence that there is an incompetent barrier to reflux. A tool for making these pressure measurements is shown in U.S. Pat. No. 4,168,703, issued to Kenigsberg.
Another test for determining whether a symptom is secondary to reflux and, therefore may be associated with GERD, is known as the Bernstein acid perfusion test. With this test, saline is dripped through a catheter that has been inserted through the patient's nose to the middle of the esophagus. Without the patient's knowledge, a dilute 0.1N hydrochloric acid solution is substituted for the saline in the catheter to see if any symptoms are triggered. The acid solution is infused until the patient experiences symptoms or for approximately twenty (20) minutes if no symptoms occur. Saline is then reintroduced into the catheter to wash out the hydrochloric acid. The catheter is used primarily because the taste of the acid solution would alert the patient to the presence of the acid. A positive result (reproduction of typical chest pain symptoms)indicates acid sensitivity in the esophageal lining. Such a positive result will typically occur in about 80% of patients with reflux. Because of the necessity of nasogastric intubation, which is uncomfortable for the patient, and the fact that this procedure must be done in a physician's office, a simpler diagnostic tool is needed.
Currently, there is no simple diagnostic test or procedure that can be done either in a physician's office or in an individual's home to assist with the diagnosis of acid reflux and GERD.